Robot system

Abstract

To provide a robot system allowing a teacher to easily teach a posture of a tool of a robot.SOLUTION: A robot system 1 includes a robot 2 having an arm 21, a sensor 3 that measures inclination angles around two axes orthogonal to each other, and a control device 4 that controls operation of the robot 2. A tool 23 is attached to the arm 21. The sensor 3 is installed on the tool 23 so as to measure inclination angles around two axes of an XT axis and a YT axis, which are orthogonal to each other in a plane on the tool 23. The control device 4 receives input of a target value related to the inclination angle around the XT axis and the YT axis, acquires a measurement value of the sensor 3 installed in the tool 23, and rotates the tool 23 around at least one of the XT axis or the YT axis such that difference between the target value and the measurement value of the sensor 3 installed in the tool 23 is equal to or less than a threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a robot system for teaching a robot. [Background technology]

[0002] A known method of teaching industrial robots is for an instructor to operate the robot on-site while teaching it. In this type of teaching, the instructor operates the robot using a teaching pendant to teach the robot the desired work content, and the robot's movements are stored in a control device.

[0003] Patent Document 1 discloses a robot teaching system applicable to the task of loading and unloading substrates into and from a cassette that stores plate-shaped substrates. A plurality of racks, each spaced at approximately equal intervals in the vertical direction, are provided inside the cassette and can support one substrate at a time. A tool (also called an end effector) for supporting the substrates is attached to the tip of the robot's arm. A teacher supports the substrates with the tool and teaches the robot how to insert and remove the substrates one by one into and from storage areas between the racks. When operating the tool in a known Cartesian coordinate system, the teacher translates the tool along three axes that make up the Cartesian coordinate system and rotates the tool around the three axes, causing the desired position and orientation to be stored in a control device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7421155 Summary of the Invention [Problem to be solved by the invention]

[0005] However, visually determining whether the tool is parallel to the rack is a difficult task even for an experienced instructor.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a robot system that allows an instructor to easily teach the posture of a tool of a robot. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a robot system including a robot having an arm, a sensor that measures tilt angles around two mutually perpendicular axes, and a control device that controls the operation of the robot, wherein a tool is attached to the arm, and the sensor is installed on the tool so as to measure the tilt angles around two mutually perpendicular axes, an XT axis and a YT axis, on a plane on the tool, and the control device receives input of target values ​​for the tilt angles around the XT axis and the YT axis, acquires measurement values ​​of the sensor installed on the tool, and rotates the tool around at least one of the XT axis or the YT axis so that the difference between the target value and the measurement value of the sensor installed on the tool is equal to or less than a threshold value.

[0008] The robot may further include a teaching pendant that receives instructions to control the operation of the robot, and the teaching pendant may be configured to receive input of a rotation angle around a vertical axis after the control device has rotated the tool around at least one of the XT axis or the YT axis.

[0009] Furthermore, the sensor may be installed on the rack to measure the tilt angle around two mutually perpendicular XR and YR axes on a plane on the rack that stores the workpieces, and the target value may be a measurement value of the sensor installed on the rack.

[0010] In addition, the control device may be configured to execute a process of rotating the tool after receiving an execution start command from an instructor, using measurement values ​​of the sensor installed on the tool obtained while the tool is stopped or in uniform linear motion. [Effects of the Invention]

[0011] The present invention provides a robot system that allows an instructor to easily teach the orientation of a tool of a robot. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an outline of a robot system according to an embodiment of the present invention. [Figure 2] A diagram that illustrates the workpiece loading operation by the robot system in Figure 1. [Figure 3] An example of sensor installation on the rack in Figure 1. [Figure 4] An example of sensor placement in the tool shown in Figure 1. [Figure 5] 1. A flowchart showing an example of the flow of a posture adjustment process performed by the control device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the embodiment of the present invention, the configuration and processing of a robot system according to the present invention will be described in detail using the teaching of a workpiece loading operation as an example. The workpiece loading operation is an operation of loading workpieces such as circuit boards into a rack one by one.

[0014] FIG. 1 is a diagram illustrating an outline of a robot system according to an embodiment of the present invention. As shown in FIG. 1, the robot system 1 includes a robot 2, a sensor 3, a control device 4 that controls the operation of the robot 2, and a teaching pendant 5 (hereinafter referred to as "TP5") that receives instructions to control the operation of the robot 2. A cassette 6 stores a plate-shaped workpiece (not shown). In FIG. 1, the cassette 6 is placed on a workbench 7.

[0015] The robot 2 has an arm 21 and a base 22 that supports the arm 21. A tool 23 is attached to the tip of the arm 21. The arm 21 is made up of a link mechanism having multiple links, and has joints that connect the links. Each joint is provided with a drive motor (not shown). The tool 23 supports and transports a workpiece. An example of the robot 2 is a vertical multi-joint robot with six joints. However, the present invention is also applicable to horizontal multi-joint robots, etc. Furthermore, the robot 2 is not limited to a single-arm robot, and may be a dual-arm robot.

[0016] The sensor 3 measures the tilt angle around two axes that are perpendicular to each other. The sensor 3 may be, for example, one biaxial tilt sensor or two single-axis tilt sensors. The sensor 3 may also be one acceleration sensor or gyro sensor with two or more axes. In FIG. 1, the sensor 3 is installed on the tool 23. As will be described later, the sensor 3 is installed not only on the tool 23 but also on the rack 61, but it is not necessary to install the sensor 3 on both the tool 23 and the rack 61 at the same time.

[0017] The CPU (Central Processing Unit) 41, memory 42, storage unit 43, and input / output I / F (interface) unit 44 of the control device 4 are connected via a bus 45. The CPU 41 reads a control program stored in advance in the storage unit 43 or the like into the memory 42 and sequentially executes a plurality of commands. The storage unit 43 is a hard disk drive, a solid state drive, or the like, and stores data used in processing described below. The input / output I / F unit 44 inputs signals from the robot 2, TP5, etc., and outputs signals to them.

[0018] The control device 4 may be built into the base 22 of the robot 2, or may be installed outside the robot 2. In the latter case, the robot 2 and the control device 4 are communicably connected via a communication cable or wirelessly. The control device 4 and TP5 are communicably connected via a communication cable or wirelessly.

[0019] The CPU (Central Processing Unit) 51, memory 52, storage unit 53, input unit 54, output unit 55, and input / output I / F (interface) unit 56 of the TP5 are connected via a bus 57. The CPU 51 reads a control program stored in advance in the storage unit 53 or the like into the memory 52 and sequentially executes a plurality of commands. The storage unit 53 is an auxiliary storage device such as a hard disk drive or solid state drive, and stores data used in the processing described below. The input unit 54 is an input device such as a physical button, a touch panel, or a microphone. The output unit 55 is an output device such as a display or a speaker. The input / output I / F unit 56 inputs signals from the control device 4 or the like, and outputs signals to them.

[0020] A plurality of racks 61 capable of supporting workpieces are provided inside the cassette 6, spaced at approximately equal intervals in the vertical direction. The space between two vertically adjacent racks 61 is a workpiece storage area 62. One workpiece storage area 62 can store one workpiece.

[0021] FIG. 2 is a diagram illustrating a workpiece loading operation performed by the robot system of FIG. 1. FIG. 2 shows a tool 23 and one rack 61. The tool 23 has a base 24 connected to the arm 21, a pair of support portions 25 and 26 extending substantially parallel from the base 24 and supporting the workpiece W, and a connecting portion 27 connecting the ends of the pair of support portions 25 and 26. The rack 61 has a back portion 63 facing the entrance for the workpiece W, and a pair of support portions 64 and 65 extending substantially parallel from the back portion 63 and supporting the workpiece W. The configurations of the tool 23 and the rack 61 are not limited to the example shown in FIG. 2.

[0022] In the workpiece loading operation, the robot 2 stops at a loading start position P1 directly facing the rack 61, with the workpiece W supported by the supports 25 and 26 of the tool 23. Next, the robot 2 moves from the loading start position P1 in a direction approaching the rack 61. Next, the robot 2 stops at a workpiece placement position P2 inside the rack 61, and then moves below the rack 61 to place the workpiece W on the supports 64 and 65. Then, the robot 2 moves in a direction away from the rack 61 and stops at a loading end position P3.

[0023] When loading multiple workpieces W one by one into the rack 61, it is effective to use a function (=shift function) that reproduces a taught operation at a shifted position in an arbitrary coordinate system. The shift function makes it easy to teach other racks 61 that differ only in height based on teaching for a reference rack 61. When using the shift function, the accuracy of the posture of the robot 2 at the loading start position P1 relative to the reference rack 61 is important. In the embodiment of the present invention, the instructor can easily teach the posture of the tool 23 at the loading start position P1 with high accuracy.

[0024] In this embodiment of the present invention, the target for adjusting the attitude of the tool 23 at the loading start position P1 is the attitude of the rack 61. Specifically, the state in which all coordinate axes of the coordinate system defined for the tool 23 and the coordinate system defined for the rack 61 are parallel at the workpiece placement position P2 is the state in which the attitude has been perfectly adjusted. Therefore, the instructor installs the sensor 3 on the rack 61 to acquire information about the target attitude. Then, the control device 4 adjusts the attitude of the robot 2 so that it matches the information about the target attitude. However, the number of degrees of freedom that can be adjusted by the control device 4 is only two of the three degrees of freedom that determine the attitude of the robot 2. The remaining degree of freedom is adjusted by the instructor via TP5.

[0025] Fig. 3 is a diagram showing an example of sensor installation on the rack of Fig. 1. Fig. 3 schematically shows one rack 61 and sensor 3. As shown in Fig. 3, sensor 3 has two axes, a-axis and b-axis, which are perpendicular to each other, and measures the tilt angle around the a-axis and the tilt angle around the b-axis. Sensor 3 is installed on rack 61 so as to measure the tilt angle around the two axes that are perpendicular to each other on a plane on rack 61.

[0026] The coordinate system of the rack 61 is, for example, a three-dimensional Cartesian coordinate system with the XR-axis, YR-axis, and ZR-axis, with the corner at the tip of the support portion 65 as the origin. The XR-axis and YR-axis are two axes that intersect at right angles on a plane on the rack 61. The ZR-axis is an axis that intersects at right angles to the plane on the rack 61. The axes of the coordinate system of the sensor 3 and the axes of the coordinate system of the rack 61 are associated, for example, by associating the a-axis with the XR-axis and the b-axis with the YR-axis. In the present invention, the plane on the rack 61 that is the target for aligning the orientation of the tool 23 does not need to be a horizontal plane (i.e., a plane perpendicular to the direction in which gravity acts), and the tool 23 can be aligned to any orientation.

[0027] At this time, the instructor can install the sensor 3 at any position on the rack 61, but install the sensor 3 so that the axis of the sensor 3 and the axis of the coordinate system of the rack 61 are as parallel as possible. In other words, the instructor installs the sensor 3 so that when the rack 61 is tilted around the XR axis, only the tilt angle of the a-axis changes, and when the rack 61 is tilted around the YR axis, only the tilt angle of the b-axis changes. The target posture information is the tilt angle of the a-axis and the tilt angle of the b-axis measured by the sensor 3 when the rack 61 is fixed in the normal position and posture.

[0028] Fig. 4 is a diagram showing an example of sensor installation on the tool of Fig. 1. Fig. 4 schematically shows the tool 23 and the sensor 3. After acquiring the target posture information, the instructor removes the sensor 3 from the rack 61 and installs it on the tool 23. The sensor 3 is installed on the tool 23 so as to measure the tilt angles around two axes that are perpendicular to each other on a plane on the tool 23.

[0029] The coordinate system of the tool 23 is, for example, a three-dimensional Cartesian coordinate system with the XT-axis, YT-axis, and ZT-axis, with the corner at the tip of the support portion 26 as the origin. The TCP (Tool Center Point) is the origin of the coordinate system of the tool 23. The TCP is a reference point for identifying the position and posture of the tool 23. The XT-axis and YT-axis are two axes that are perpendicular to each other on a plane on the tool 23. The ZT-axis is an axis that is perpendicular to the plane on the tool 23. The axes of the sensor 3 are associated with the axes of the coordinate system of the tool 23 in the same way as when the sensor 3 is installed on the rack 61, with the a-axis corresponding to the XT-axis and the b-axis corresponding to the YT-axis.

[0030] At this time, the instructor can install the sensor 3 at any position on the tool 23, but install the sensor 3 so that the axes of the coordinate system of the sensor 3 and the axes of the coordinate system of the tool 23 are as parallel as possible. In other words, the instructor installs the sensor 3 so that when the tool 23 is rotated around the XT axis, only the tilt angle of the a axis changes, and when the tool 23 is rotated around the YT axis, only the tilt angle of the b axis changes.

[0031] FIG. 5 is a flowchart showing an example of the flow of the posture adjustment process performed by the control device of FIG. 1. In the example shown in FIG. 5, teaching is performed at multiple positions. As shown in FIG. 5, the control device 4 receives input of target values ​​for the tilt angles around the XT-axis and the YT-axis (step S1). As described above in the description of FIG. 3, the target values ​​are measurement values ​​(= the tilt angles of the a-axis and the b-axis) measured by the sensor 3 installed on the rack 61. For example, the TP5 may receive input of the target values ​​from an instructor and transmit the input target values ​​to the control device 4. Alternatively, for example, if the sensor 3 and the control device 4 are connected to each other so as to be able to communicate via a communication cable or wirelessly, the sensor 3 may transmit the target values ​​to the control device 4. Then, the control device 4 controls the operation of the robot 2 to translate the TCP position to the target position in accordance with the instructor's jog operation via the TP5 (step S2).

[0032] Next, the control device 4 checks whether or not the execution condition for the posture adjustment process is satisfied (step S3). The execution condition for the posture adjustment process is that an instruction to start the process is given by the instructor. If necessary, the control device 4 may also check whether a predetermined judgment condition is satisfied. In this case, the execution condition for the posture adjustment process is an AND condition of the instruction to start the process given by the instructor and the satisfaction of the predetermined judgment condition.

[0033] The reception of an execution start command from the instructor will now be described. The TP5 may display an operation screen (not shown) on a display where an execution button for the posture adjustment process is arranged, and may receive a button press from the instructor via a touch panel. Alternatively, the TP5 may have a physical execution button for the posture adjustment process, and may receive a physical button press from the instructor. Alternatively, the TP5 may receive an execution start command by voice via a microphone. In either case, the TP5 transmits to the control device 4 that an execution start command has been issued. As a result, the control device 4 receives the execution start command from the instructor.

[0034] Next, confirmation of predetermined judgment conditions by the control device 4 will be described. If the acceleration components other than gravity with respect to the tool 23 are not zero, the measurement values ​​of the sensor 3 attached to the tool 23 cannot be correctly acquired. Therefore, the control device 4 may receive an execution start command from the instructor, confirm that the tool 23 is stopped or in uniform linear motion, and immediately thereafter acquire the measurement values ​​of the sensor 3 attached to the tool 23. Alternatively, the control device 4 may constantly acquire the measurement values ​​of the sensor 3 attached to the tool 23, and execute subsequent processing using the measurement values ​​when it is confirmed that the tool 23 is stopped or in uniform linear motion.

[0035] For example, the control device 4 may calculate the velocity in the TCP based on the output value of an encoder (not shown) that detects the rotation angle of the drive motor of each joint of the robot 2 and a Jacobian matrix determined by the mechanism of the robot 2, and refer to the value of the amount of change. Also, for example, if the sensor 3 is capable of measuring acceleration in three axes, the control device 4 may refer to the acceleration value measured by the sensor 3. Then, based on these values, the control device 4 confirms that the tool 23 is stopped or in uniform linear motion.

[0036] If the tool 23 is neither stopped nor moving at a constant speed in a straight line, the control device 4 may send a stop command to the robot 2 to satisfy the execution condition. Also, instead of checking whether the tool 23 is stopped or moving at a constant speed in a straight line, the control device 4 may send a stop command to the robot 2 when an execution start command is issued by the instructor.

[0037] Furthermore, in order to reduce the effects of disturbances and vibrations and to prevent abnormal operation of the robot 2, the control device 4 may confirm that the maximum change and variance in the measurement values ​​of the sensor 3 over a predetermined time period are equal to or less than threshold values. In this case, the control device 4 receives an execution start command from the instructor, and after confirming that the tool 23 is stopped or in uniform linear motion and that the maximum change and variance in the measurement values ​​of the sensor 3 over a predetermined time period are equal to or less than threshold values, executes the subsequent step S4.

[0038] Returning to the description of the flowchart in Fig. 5, if the execution condition is not met (No in step S3), the control device 4 repeats the process from step S3, and if the execution condition is met (Yes in step S3), the control device 4 proceeds to step S4.

[0039] Next, the control device 4 acquires the measurement values ​​of the sensor 3 installed on the tool 23 (step S4). The measurement values ​​of the sensor 3 are the tilt angle of the a-axis and the tilt angle of the b-axis. Then, the control device 4 receives an execution start command from the instructor via TP5 (step S5). The control device 4 does not execute the process for automatically controlling the robot 2 unless an execution start command is issued by the instructor.

[0040] Next, the control device 4 rotates the tool 23 around the XT axis and the YT axis so that the difference between the target value received in step S2 and the measurement value of the sensor 3 acquired in step S4 becomes equal to or less than a threshold value. Specifically, the control device 4 calculates each axis angle of the robot 2 that makes the difference between the target value and the measurement value zero (step S6). Next, the control device 4 transmits to the robot 2, with the position of the TCP fixed, a command to rotate each joint of the robot 2 in accordance with each axis angle calculated by the step execution start command (step S7). Then, the robot 2 rotates each joint of the robot 2 in accordance with the command received from the control device 4.

[0041] The calculation of each axis angle of the robot 2 will be described. The control device 4 pre-stores a homogeneous transformation matrix represented by the link parameters of the robot 2. Link parameters that use the Denavit-Hartenberg notation (DH method) are known and are also called DH parameters. The pre-stored link parameters are the link distance, link torsion angle, and link length, and are treated as constants. The remaining link parameters, the link angles, correspond to the axis angles and are treated as variables. For example, if the robot 2 is a six-axis vertical articulated robot with seven links and coordinate systems at both ends of the links, there will be eight coordinate systems. The coordinate system at one end is the base coordinate system (also called the machine coordinate system or robot coordinate system), which is set on the mounting surface of the base 22. The coordinate system at the other end is the tool coordinate system, which is set on the tool 23. The link parameters represent the relationship between adjacent coordinate systems. The homogeneous transformation matrix from the base coordinate system of the robot 2 to the tool coordinate system is expressed by the following equation.

[0042]

number

[0043] Furthermore, the calculation for rotating the tool 23 around the tool coordinate axis while keeping the position of the TCP fixed is performed by multiplying the homogeneous transformation matrix of equation (1) by a homogeneous transformation matrix of only the rotational component, as expressed by the following equation.

[0044]

number

[0045] Here, the a-axis corresponds to the XT-axis, and the b-axis corresponds to the YT-axis, as shown in Fig. 4. The control device 4 converts the difference between the target values ​​and measured values ​​for the tilt angles of the a- and b-axes into a rotation matrix R', and calculates the angle of each axis by solving the inverse kinematics problem related to equation (2).

[0046] Then, the control device 4 transmits to the robot 2 a command to rotate each joint at a low speed based on each calculated axis angle. Upon receiving the command from the control device 4, the robot 2 rotates the tool 23 around each axis in accordance with the command.

[0047] After the robot 2 rotates the tool 23 around the XT axis and the YT axis, the control device 4 may again acquire the measurement value of the sensor 3 installed on the tool 23 and calculate the difference between the target value and the measurement value. If the difference between the target value and the measurement value is equal to or greater than a predetermined threshold, the control device 4 may repeatedly execute the processes of steps S6 and S7. Alternatively, the control device 4 may preset a rotation angle (amount of change) for one rotation and repeat the processes until the difference between the target value and the current measurement value of the sensor 3 becomes equal to or less than the predetermined threshold.

[0048] The calculation process for each axis angle of the robot 2 is not limited to analytical solutions, but may also use numerical solutions that calculate numerical solutions by iterative calculation algorithms using Jacobian matrices, etc. However, analytical solutions can be performed with higher accuracy and in a shorter time.

[0049] When the processing up to step S7 is completed, the two degrees of freedom that determine the attitude of the tool 23, i.e., the orientation of the tool 23 around the XT and YT axes, are adjusted to match the target values. In this state, the plane formed by the XT and YT axes and the plane formed by the XR and YR axes are approximately parallel. In the embodiment of the present invention, the remaining degree of freedom that determines the attitude of the tool 23 is adjusted by rotating the tool 23 around an axis in the vertical direction (= the direction in which gravity acts).

[0050] If the tool 23 were to be rotated around the ZT axis, the measurement values ​​of the sensor 3 installed on the tool 23 would change, causing the orientations around the XT and YT axes to deviate from the target values. In this case, it would be necessary to repeatedly adjust the orientations around the XT and YT axes and the ZT axis, which would be inconvenient. In the embodiment of the present invention, the tool 23 is rotated around a vertical axis, so the measurement values ​​of the sensor 3 installed on the tool 23 do not change, and the orientations of the tool 23 around the XT and YT axes can be maintained in agreement with the target values.

[0051] Furthermore, adjustment of the orientation around the vertical axis is instructed by the instructor via TP5. The instructor only needs to adjust the remaining one degree of freedom while the other two degrees of freedom that determine the attitude of the tool 23 are correct, making the adjustment easy.

[0052] Returning to the description of the flowchart in Fig. 5, the control device 4 receives an input of a rotation angle around a vertical axis (step S8). For example, the TP5 receives an input of a rotation angle around a vertical axis from an instructor and transmits the input rotation angle around the vertical axis to the control device 4.

[0053] Next, with the position of the TCP fixed, the control device 4 transmits to the robot 2 a command to rotate the joint of the robot 2 in accordance with the rotation angle input in step S8 (step S9). Upon receiving the command from the control device 4, the robot 2 rotates the tool 23 around an axis in the vertical direction in accordance with the command.

[0054] The processing of step S9 will be described. In step S9, the control device 4 executes rotation of the tool 23 around the coordinate axes of a coordinate system obtained by translating the base coordinate system to the TCP origin. As a result, if any axis of the base coordinate system coincides with the vertical direction, rotation of the tool 23 around an axis in the vertical direction can be realized. The homogeneous transformation matrix when the tool 23 is rotated around the coordinate axes of the coordinate system obtained by translating the base coordinate system to the TCP origin can be found by the following equation. Furthermore, each axis angle can be calculated by finding an inverse kinematic solution.

[0055]

number

[0056] When the base 22 of the robot 2 is installed on a floor surface perpendicular to the vertical direction, the measurement value of the sensor 3 installed on the tool 23 does not change when the base coordinate system rotates around the vertically upward axis.

[0057] Returning to the explanation of the flowchart in Fig. 5, fine adjustments to the position and orientation of the tool 23 are made as necessary. Then, the control device 4 executes a position and orientation recording process in accordance with instructions from the instructor (step S10). Specifically, upon receiving a recording command from the instructor via TP5, the control device 4 stores information on the position and orientation of the tool 23 at the current passing point in the storage unit.

[0058] Next, the control device 4 confirms with the instructor whether or not to teach the next position (step S11). If teaching the next position (Yes in step S11), the control device 4 repeats the process from step S2. If teaching the next position is not to be performed (No in step S11), the control device 4 ends the process.

[0059] While the above description has been given using a workpiece loading operation as an example, the embodiment of the present invention can also be applied to a workpiece unloading operation in which workpieces W, such as circuit boards, are unloaded one by one from a cassette 6. Furthermore, the workpiece W is not limited to circuit boards, but is not particularly limited to any object that can be handled by an industrial robot. Furthermore, the source and destination of the workpiece W are not limited to the rack 61, but are not particularly limited to any object that can be handled by an industrial robot. Furthermore, the embodiment of the present invention is not limited to workpiece loading and unloading operations, but can also be applied to assembly operations such as inserting a cylindrical workpiece W into a cylindrical hole. If it is not possible to install the sensor 3 in the same location as described above, the sensor 3 can be installed in a location where the orientation of the workpiece W, its source, and its destination does not change relative to each other, and the target value of the orientation information can be acquired.

[0060] As described above, in the robot system 1 according to the embodiment of the present invention, the tool 23 is attached to the arm 21, and the sensor 3 is installed on the tool 23 so as to measure the tilt angles around two mutually perpendicular axes, the XT axis and the YT axis, on a plane of the tool 23. The control device 4 receives input of target values ​​for the tilt angles around the XT axis and the YT axis, and acquires the measurement values ​​of the sensor 3 installed on the tool 23. The control device 4 then rotates the tool 23 around at least one of the XT axis or the YT axis so that the difference between the target value and the measurement value of the sensor 3 installed on the tool 23 is equal to or less than a threshold value. This makes it possible to automatically adjust at least one degree of freedom that determines the attitude of the tool 23, allowing an instructor to easily teach the attitude of the tool 23.

[0061] The robot system 1 also includes a TP5 that receives instructions to control the operation of the robot 2. The TP5 receives input of a rotation angle about a vertical axis after the control device 4 rotates the tool 23 about at least one of the XT axis and the YT axis. By rotating the tool 23 according to the input rotation angle about the vertical axis, the measurement value of the sensor 3 installed on the tool 23 does not change, and the orientation of the tool 23 about the XT axis or the YT axis can be maintained in a state that matches the target value.

[0062] Furthermore, the sensor 3 is installed on the rack 61 storing the workpiece W so as to measure the tilt angle around two mutually perpendicular axes, the XR axis and the YR axis, on a plane on the rack 61. The target value is the measurement value of the sensor 3 installed on the rack 61. This allows the instructor to teach the posture of the tool 23 during the workpiece loading and unloading operations with high precision. In particular, since the sensor 3 does not need to be installed on both the rack 61 and the tool 23 at the same time, one sensor 3 capable of measuring two or more axes, or two sensors 3 measuring only one axis, is sufficient. Furthermore, even if there are multiple racks 61, the same sensor 3 can be used, which makes it extremely cost-effective.

[0063] Furthermore, the control device 4 executes a process of rotating the tool 23 after receiving an execution start command from the instructor, using the measurement values ​​of the sensor 3 attached to the tool 23 acquired while the tool 23 is stopped or moving in a uniform linear motion. This allows the control device 4 to use accurate measurement values ​​of the sensor 3 and to safely control the robot 2.

[0064] While the preferred embodiments of the robot system and the like according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas disclosed herein, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0065] 1. Robot system 2. Robot 3. Sensor 4. Control device 5. Teaching pendant (TP) 6...Cassette 21...Arm 23...Tools 61...Rack W...Work

Claims

1. A robot system comprising: a robot having an arm; a sensor for measuring tilt angles around two axes perpendicular to each other; and a control device for controlling the operation of the robot, A tool is attached to the arm; the sensor is installed on the tool so as to measure the tilt angle around two mutually orthogonal axes, an XT axis and a YT axis, on a plane on the tool; The control device receives input of target values ​​for the tilt angles around the XT axis and the YT axis, acquires measurement values ​​of the sensors installed on the tool, and rotates the tool around at least one of the XT axis and the YT axis so that a difference between the target value and the measurement value of the sensor installed on the tool becomes equal to or less than a threshold value. A robot system characterized by:

2. a teaching pendant that receives instructions to control the operation of the robot; The teaching pendant receives an input of a rotation angle around a vertical axis after the control device rotates the tool around at least one of the XT axis and the YT axis.

2. The robot system according to claim 1.

3. the sensor is installed on the rack storing the workpiece so as to measure the tilt angle around two axes, an XR axis and a YR axis, which are perpendicular to each other on a plane on the rack; The target value is a measurement value of the sensor installed on the rack.

3. The robot system according to claim 1 or 2.

4. The control device executes a process of rotating the tool after receiving an execution start command from an instructor, using the measurement values ​​of the sensor installed on the tool that are acquired while the tool is stopped or in uniform linear motion.

3. The robot system according to claim 1 or 2.

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